The objective of this proposal is to study two genes, Prt and Lpq, that appear to be linked to the rabbit immunoglobulin kappa light chain gene, Ab. We will first attempt to show that the two genes are truely linked and not just guasi-linked to the Ab gene by doing appropriate crosses. We will then isolate and characterize the two genes' products using standard biochemical methods. Finally, using immunofluorescene techniques we will study the regulation of the genes in the tissues in which they are expressed. By studying the regulation of the genes, we hope to determine if allelic exclusion is a property of a single gene (i. e., affects only the Ab gene) or if allelic exclusion is a property of the chromosome or a segment of the chromosome (i. e., affects two or more of the genes in the linkage group). Preliminary evidence, suggesting that allelic exclusion is a property of the Lpq gene, indicates that allelic exclusion is a property of the chromosome. Finding allelic exclusion for several genes in the linkage group would suggest that there is a mechanism for inactivating regions of the chromosome. This mechanism may be similar to gene inactivation of heterochromatization that is associated with the X-chromosome genes.